1. Field of the Invention
This invention relates to a non-circular gear pair applicable to a non-step variable speed gear in a power transmission gear device.
2. Description of the Prior Art
One example of a non-circular gear pair applicable to a non-step variable speed gear has been disclosed by Japanese Patent Application (OPI) No. 266866/1986 (the term "OPI" as used herein means an "unexamined published application") which has been filed by the present applicant. The non-circular gear pair has intermeshing pitch curves which include a part which has a positive constant value K which is defined as follows, and a part which has a negative constant K: EQU K=d log F(.theta.)/d.theta.
where .theta. is the angular displacement of one of two engaged non-circular gears forming the non-circular gear pair, and F(.theta.) is the rotation speed ratio of the two gears. And it has disclosed a non-step variable speed gear as its application which is formed by using gear units each comprising three or four of such non-circular gears.
In the above-described conventional non-circular gear pair, the part of positive constant value K and the par of negative constant value K are successively provided on the intermeshing pitch curves. Therefore, the intermeshing pitch curves have a point where the rotation speed ratio (.theta.) cannot be differentiated, that is, the angular acceleration ratio changes discontinuously. When the gears are intermeshed at this point, an inertial force is abruptly produced in the variable speed gear, so that the latter is vibrated with the result that its efficiency is lowered.